LV - Low Vision Exam I - Week 2 Flashcards
List the 9 components of a low vision exam.
History including goals VA Refraction and BCVA Contrast sensitivity Visual fields Lighting/glare Magnification Non-optical aids/devices Management
List and describe 5 general observations that could be made during history in a low vision exam.
Mobility
-use of any devices/assistance, recognition of doorways etc
Fixation
-head positioning, eye-contact when talking, eccentric fixation, nystagmus
Cosmesis
-ptosis, scarring, prosthesis
Physical
-other problems such as hearing loss, tremors, general health appearance
Psychological
-attitude, cognitive status, independence, people who accompany them
List 6 things to ask about for vision and ocular history during a low vision exam.
Explore vision loss (onset, progression, cause, etc) Current eye-care and by whom Last review Any previous treatment Current spectacles, prescribed date Special aids
How much does a 6m letter subtend at 6m, how much does a limb subtend, and what is the height in mm?
6 m letter subtends 5’ arc, limbs subtend 1’ at 6 m and is 8.7 mm in height
How much magnification is every three lines? What about six and nine lines?
3 - 2x mag
6 - 4x mag
9 - 8x mag
What is the formula for the magnification required to see a specific line on a logMAR chart? Give an example with 6/24 to read 6/6.
Mag required = letters read / letters they wish to read
-if a patient has 6/24, x4 telescope is needed to achieve 6 lines to 6/6
What viewing distance is advised for low vision exams? What should you do when recording?
Reduce viewing distance - 2.4m, 1.2m
Record using actual distance as snellen numerator (2.4/x) then convert to standard 6/x
How many lines of improvement is considered worth prescribing spectacles for?
Three or more
Describe how N8 print subtends at 1m. What is this notation called? How is it converted to the N notation?
Has a loop height that subtends 5’ a the eye for viewing distance of 1m
At 25cm, M = N/8
What snellen line is N20 at 25cm equivalent to?
6/60
Describe how to convert from N to snellen at 25cm.
At 25cm, denominator of snellen is Nx3
-N8 at 25cm is 6/24
True or false
Most low vision patients tend to be monocular
Explain your answer.
True
-due to large difference in acuity of each eye
How can you tell if patients are binocular or monocular?
If their VA is better binocularly, then likely binocular
If their binocular VA is the same as their best eye VA, likly they are suppressing the poorer eye
Is it possible for binocular VA to be worse than monocular VA? Explain your answer.
Yes it is - likely retinal rivalry is occurring
-occlude poorer eye
With how many lines of difference between the eyes should you begin to investigate binocularity? List two ways.
3 lines or less
Worth 4 dot test
Bar reading test
